302 Notes and Comments. 
carried out under his direction in the Irish Sea off the Isle of 
Man during April, 1907, with the object of testing different 
kinds of open and closing tow-nets and of gathering information 
as to the detailed distribution of the organisms according to the 
length, depth, and date. Examples were given of very different 
results both quantitative and qualitative to those from quite 
similar casts taken not far apart either in space or time. 
Sudden variations in horizontal distribution of the Plankton 
were discussed, and seasonal changes were also considered. 
The necessity of numerous gatherings in well-chosen restricted 
areas was emphasised. His conclusions were (1) That they 
must investigate their methods before they attempted to investi- 
gate on a largescale. (2) That they must find out much about 
their gathering of organisms before they could consider them 
as adequate samples ; and (3) that they must make an intensive 
study of small areas before they drew conclusions in regard to 
relatively large regions such as the North Sea or the Atlantic 
Ocean. 
MIMICRY IN. INSECTS. 
At one of the evening meetings at the British Association, 
Dr. F. A. Dixey gave a discourse on ‘‘ Recent Developments 
in the Theory of Mimicry.” Dr. Dixey, at the outset, observed 
that the remarkable resemblances that existed between 
certain insects belonging to widely different orders, as, for 
instance, the likeness borne by some of the ‘‘clear-wing 
moths”? to wasps and hornets, had long been known to 
naturalists. They were interpreted by the older observers as 
cases of ‘‘repetition,” and ‘‘analogy” in nature. Kirby and 
Spence were the first to attempt a rational explanation. These 
authors got so far as to suggest that one species might gain an 
advantage by resembling another ; but the first really scientific 
account of the matter was given by Bates, who pointed out 
that certain kinds of butterflies in South America escaped 
attacks from birds by mimicking the appearance of other 
conspicuous species which were immune from persecution on 
account of the possession of distasteful qualities. This 
resemblance to a distasteful model he considered had been 
gained by a gradual increase of forms tending in the 
necessary direction. Bates’ theory of mimicry, which was 
at once accepted by Darwin, and met with general approval, 
marked an important step in advance, but left certain facts 
unexplained. The lecturer then discussed the further contri- 
, 
Naturalist, 
